The tremendous growth in the use of cordless telecommunications systems has increased the demand for a system having high capacity, high quality communications and small, inexpensive subscriber units. The basis for these characteristics is primarily low power digital transmission and small micro-cells. As low power technology advances, the limitations will be the transmit power and/or the feasibility of smaller cells. Of course, these limitations have inherent problems as well as inherent benefits.
If the transmit power in a portable subscriber unit is reduced, the likelihood of decreased range and cell size naturally follows. Use in densely populated areas such as urban and indoor environments results in greater multipath effects. This would limit the data rates available for use within the system. Decreased cell size would result in more base station sites, greater infra-structure, and an increased number of handoffs between cells. Other system problems may exists as well, including the ability to implement a portable controlled handoff, and compensating for an unexpected propagation environment (e.g., irregular cell shapes, moving objects, etc.). Therefore, a need for compensating for these limitations exists.
Using a directional antenna provides increased system gain in a limited direction by reducing the system gain in other directions. The use of a plurality of antennas and/or a means of steering a given number of antennas in addition to measuring signal quality (in a given direction) would allow the selection of a particular direction to achieve improved system gain. Antenna arrays are typically used to steer an antenna beam electronically. The array typically consists of antenna elements such as dipoles or slots, waveguides or horns, and microstrip antennas or other configurations. These arrays can be electronically steered by phase shifting the reception or transmission signal. Of course, other means of steering an antenna (including mechanically rotating) would be within contemplation of the present invention.